Train travel can be safe for most women who are pregnant, even though it can be quite uncomfortable. One of the major discomforts is morning sickness that occurs during the first trimester, but those who find they are pregnant should wait until later in the pregnancy (second trimester) because train movement might make the women nauseous.
Pregnant women also have to take into consideration the type of train they plan to ride. If the train does not have air conditioning and jostles quite a bit, this can be very uncomfortable for the woman. Conversely, a train that has air conditioning and runs smoothly will not create bumps or much discomfort.
Ultimately, women who are pregnant (especially those who have had complications early in their pregnancy) should consult their physician before taking a trip. The medical professional will be able to better ascertain the condition of the mother and whether she would be able to ride safely. After getting the approval of a physician, the choice to take a train ride is up to the mother.